The present invention generally relates to the field of electrical signal processing circuitry, and more particularly to the use of such circuitry for controlling the dwell and spark ignition in an ignition system for an internal combustion engine.
It has been recognized that the present day mechanical ignition systems for automobiles and similar vehicles cannot meet the requirement for reliably controlling the spark timing and dwell of an internal combustion engine over the estimated lifetime of the engine. Thus many prior art solid state ignition systems have been proposed for electronically controlling the dwell and spark ignition of an internal combustion engine and thereby conserving fuel and reducing pollution by increasing the efficiency of the engine.
Generally, most prior art electronic ignition systems utilize a crankshaft position sensor for synchronizing developed electronic control signals to predetermined positions of the engine crankshaft. However, generally the accuracy of the prior art electronic ignition systems is severely dependent upon the duty cycle of the crankshaft position sensor signal. Since the duty cycle of the sensor signal (the ratio of one logic state produced by the sensor to the period of the sensor signal) may vary substantially under certain engine conditions, the prior art electronic ignition systems have been unable to utilize the sensor signal to accurately control the dwell and spark timing of the engine with the precision which is desired.
In addition, most prior art electronic ignition systems are unable to initiate dwell at a precise time before the occurrence of a crankshaft sensor position pulse. The prior art systems have also generally been unable to accurately monitor the engine speed and update this speed monitoring information during each crankshaft rotation.
Thus while the prior art electronic ignition systems have avoided some of the disadvantages of the mechanical ignition systems caused by the wearing out of mechanical parts, the accuracy of prior art electronic ignition systems leaves much to be desired.